The present invention relates to an infrared-ray radiating lamp intended for installation on an automobile which radiates infrared rays onto a region in front of the automobile and, more particularly, to such an infrared-ray radiating lamp which is used in combination with a CCD camera having a sensitivity covering the near-infrared range to provide the driver of the vehicle in which the system is mounted a nighttime view of regions including areas beyond those illuminated by the headlamps of the vehicle.
A conventional lamp of this type has an infrared-ray transmitting globe having a surface coated with an infrared-ray transmitting multilayer film disposed so as to cover an infrared/visible-ray source in a lighting chamber defined by a lamp body and a front lens. Infrared rays emitted by the source and transmitted through the globe are reflected by a reflector, transmitted by the front lens and distributed forwards. A CCD camera, which is disposed in a front portion of a vehicle and has sensitivity covering the near-infrared range, images an infrared-ray radiating region in front of the vehicle. The image of this region is processed by an image processor and displayed on a monitor screen in the passenger compartment to thus provide the driver with a view of the scene ahead. The driver can recognize on the monitor screen the presence of objects such as persons, lane-markers and obstacles in the far distance.
However, there is a problem with the aforementioned conventional infrared-ray radiating lamp in that since the infrared-ray transmitting multilayer film cannot completely cut visible rays having relatively long wavelengths in the range of 700 to 800 nm, the lamp appears illuminated in red. This creates the possibility of mistaking the infrared-ray radiating lamp disposed at the front of the vehicle for a tail lamp or a stop lamp, thus causing a safety problem.
The invention has been made in consideration of the above-mentioned problem of the conventional art. It is, therefore, an object of the invention to provide an infrared-ray radiating lamp that cannot be mistaken for a tail lamp or a stop lamp by ensuring that not only infrared rays but also visible rays are emanated from a front lens simultaneously.
To achieve the aforementioned object, an infrared-ray radiating lamp for an automobile according the invention comprises a lighting chamber defined by a lamp body and a front lens, a reflector disposed in the lighting chamber, and infrared-ray radiation means and visible-ray radiation means disposed in front of the reflector in the lighting chamber, and is constructed so that infrared rays radiated from the infrared-ray radiation means and visible rays radiated from the visible-ray radiation means are emanated from the front lens simultaneously.
When the lamp is illuminated, the infrared rays radiated from the infrared ray radiation means and the visible rays radiated from the visible ray radiation means are reflected by the reflector and emanated from the front lens simultaneously. Thus, the rays radiated by the lamp include both infrared rays and white visible rays. Therefore, the red color is unnoticeable in comparison with the conventional lamp, which mainly radiates infrared rays and appears illuminated in red.
The infrared-ray radiating lamp may be provided with radiation control means for controlling the radiation and the stopping of radiation of infrared rays by at least the infrared-ray radiation means, wherein the radiation control means stops the radiation of infrared rays when the vehicle speed is equal to or lower than a predetermined speed.
Human eyes can be damaged by continuous exposure to infrared rays, which is certainly an undesirable situation. To prevent such damage, if the vehicle speed is so low that the eyes of pedestrians, etc., within the radiation zone of the lamp might be continuously exposed to the infrared rays from the infrared-ray radiating lamp, the radiation control means stops at least the radiation of infrared rays by the infrared-ray radiation means as soon as it is judged, based on speed information obtained from the output of the vehicle speed sensor, that the vehicle speed has become equal to or lower than the predetermined speed.
The infrared-ray radiation means is preferably composed of an infrared/visible-ray source, namely, a source which emits both infrared and visible rays, and an infrared-ray transmitting film partially covering the infrared/visible-ray source, while the visible-ray radiation means is composed of a visible-ray transmitting portion of the infrared/visible-ray source where there is no infrared-ray transmitting film.
The infrared rays from the infrared/visible-ray source are transmitted by the infrared-ray transmitting film, reflected by the reflector, and emanated from the front lens. Simultaneously, the visible rays from the infrared/visible-ray source are transmitted by the visible-ray transmitting portion, reflected by the reflector and emanated from the front lens. As a result, the rays distributed by the lamp include both infrared rays and white visible rays, and therefore the red color is not particularly noticeable.
The infrared-ray transmitting film may be disposed on the outer surface of a glass bulb forming the infrared/visible-ray source. The infrared-ray radiating lamp can be constructed by employing as a light source an infrared/visible-ray radiating bulb having the infrared-ray transmitting film disposed on the outer surface of the glass bulb. The infrared-ray radiating lamp can also be constructed by providing a globe having an infrared-ray transmitting film on its outer surface which covers the bulb forming the infrared/visible-ray source.
The infrared-ray radiating lamp may be constructed so that the globe is longitudinally displaceable between a rearward position on the optical path of rays traveling from the infrared/visible-ray source towards the reflector and a forward position in front of the infrared/visible-ray source. In such a case, when the globe is in the rearward position, the infrared rays from the infrared/visible-ray source are transmitted by the infrared-ray transmitting film of the globe, reflected by the reflector, and distributed forwards, and the visible rays from the infrared/visible-ray source are transmitted by the visible-ray transmitting portion, namely, the region of the globe where there is no infrared-ray transmitting film, reflected by the reflector and distributed forwards. As a result, the rays distributed by the lamp include both infrared rays and visible rays, and therefore the red color is not particularly noticeable. When the globe assumes the forward position, the rays emitted from the infrared/visible-ray source are directly reflected by the reflector and distributed forwards. As a result, the rays distributed by the lamp mainly include visible rays.
Further, the infrared-ray radiation means may be composed of an infrared/visible-ray source and an infrared-ray transmitting film covering the infrared/visible-ray source, and that the visible-ray radiation means may be constructed of an auxiliary bulb disposed in front of the reflector in the lighting chamber. In this case, the infrared rays from the infrared/visible-ray source are transmitted by the infrared-ray transmitting film, reflected by the reflector and emanated from the front lens. Simultaneously, the rays (visible rays) emitted from the auxiliary bulb are reflected by the reflector and emanated from the front lens. As a result, the rays distributed by the lamp include both red infrared rays and white visible rays, and therefore the red color is not particularly noticeable.
The reflector may be composed of an elliptical mirror at the center and a parabolic mirror disposed outside the elliptical mirror. The infrared-ray radiation means may be composed of the elliptical mirror, with the infrared/visible-ray source disposed in the proximity of a first focus of the elliptical mirror, a projection lens disposed in front of the infrared/visible-ray source, and an infrared-ray transmitting filter disposed between the infrared/visible-ray source and the projection lens. The visible-ray radiation means is composed of the infrared/visible-ray source and the parabolic mirror.
With this construction, the infrared rays from the infrared/visible-ray source, which have been reflected by the elliptical mirror so as to converge at the second focus, are transmitted by the infrared-ray transmitting filter prior to reaching the projection lens, projected and distributed forwards by the projection lens, and thus emanated from the front lens. On the other hand, the visible rays emitted by the infrared/visible-ray source, which have been reflected by the parabolic mirror, are also emanated from the front lens simultaneously with the infrared rays. As a result, the rays emitted by the lamp include both infrared rays and white visible rays, and therefore the red color is not particularly noticeable.